thermal bridge

Last month, Joe Lstiburek gave the fifth annual Twitterview † from his crawl space. (Peter Troast of Energy Circle has published the transcript of this year’s event.) One of the pearls of wisdom dispensed by Joe was that, “Passivhaus is the only place where real innovation is happening.”

Amy Musser has a PhD in Architectural Engineering and, like me, used to be a college professor. Her husband, Matthew Vande, is an architect with an MS in Architectural Engineering. He is also a treehugger (see the black and white photo below). Together, they founded Vandemusser Design, a firm that provides green design, certification, and consulting.

Like wind washing, thermal bridging is something folks mention all the time during audits (meaning they never ask about it). But what is thermal bridging, and why do I keep bringing it up when my customers just want new windows?
To understand thermal bridging, you need to understand your home’s wall assembly and the various materials used in its construction.

Let's play a little game today. Take a look at that photo at right. See anything that bothers you?* Well, pretend that you're the heat in the house once everything is finished and people are living in it. Does that help? If your answer is still no, let me give you a little help. Here are the approximate R-values of wood and the standard insulation you might find in a wall (fiberglass, cellulose, open-cell spray foam):

Sal Lombardo is planning a new home in the New York-New Jersey area (Climate Zone 5) and is looking at a long list of high-performance construction options: double-stud walls, structural insulated panels, insulating concrete forms, Larsen trusses, and walls built with light-gauge steel framing.
Wait a minute. Steel framing, as in the stuff that leaks heat through the building envelope like a proverbial sieve? Maybe, Lombardo says, it deserves another look.